Add stats for frequency offset when converting RTP timestamp to NTP time.

webrtc/video/receive_statistics_proxy.h

Index: webrtc/video/receive_statistics_proxy.h
diff --git a/webrtc/video/receive_statistics_proxy.h b/webrtc/video/receive_statistics_proxy.h
index 4c6caf0daa0cba927108ab5d39733bc04c590d82..c6dcfb974b969e371a9d8eb4debff13ca7284c1a 100644
--- a/webrtc/video/receive_statistics_proxy.h
+++ b/webrtc/video/receive_statistics_proxy.h
@@ -22,6 +22,7 @@
 #include "webrtc/common_video/include/frame_callback.h"
 #include "webrtc/modules/video_coding/include/video_coding_defines.h"
 #include "webrtc/video/report_block_stats.h"
+#include "webrtc/video/stats_counter.h"
 #include "webrtc/video/video_stream_decoder.h"
 #include "webrtc/video_receive_stream.h"
 
@@ -44,7 +45,7 @@ class ReceiveStatisticsProxy : public VCMReceiveStatisticsCallback,
   VideoReceiveStream::Stats GetStats() const;
 
   void OnDecodedFrame();
-  void OnSyncOffsetUpdated(int64_t sync_offset_ms);
+  void OnSyncOffsetUpdated(int64_t sync_offset_ms, double estimated_freq_khz);
   void OnRenderedFrame(const VideoFrame& frame);
   void OnIncomingPayloadType(int payload_type);
   void OnDecoderImplementationName(const char* implementation_name);
@@ -121,6 +122,7 @@ class ReceiveStatisticsProxy : public VCMReceiveStatisticsCallback,
   SampleCounter current_delay_counter_ GUARDED_BY(crit_);
   SampleCounter delay_counter_ GUARDED_BY(crit_);
   SampleCounter e2e_delay_counter_ GUARDED_BY(crit_);
+  MaxCounter freq_offset_counter_ GUARDED_BY(crit_);
   ReportBlockStats report_block_stats_ GUARDED_BY(crit_);
   QpCounters qp_counters_;  // Only accessed on the decoding thread.
   std::map<uint32_t, StreamDataCounters> rtx_stats_ GUARDED_BY(crit_);